cNa+(P) is the concentration of sodium (Na+) in plasma. The systematic symbol for arterial blood is cNa+(aP). The analyzer symbol may be Na+ or cNa+.
What does cNa+ tell you
The body has a total sodium level of about 60 mmol/kg, the majority of which is divided between the bone and the extracellular fluid.
The plasma level of about 140 mmol/L is regulated by the plasma content of sodium, water, and intracellular potassium. Therefore, high plasma sodium may be due to low body water - or vice versa. It represents about 90 % of the inorganic cations in plasma, making it responsible for almost half the osmolality of the plasma.
cNa+(aP) reference range (adult): 136-146
A. Low values of cNa+ can be caused by:
- Water intoxication
- Renal failure
- Heart failure
- Liver failure
- Increased ADH secretion
- Nephrotic syndrome
B. High values of cNa+ can be caused by:
- Increased sodium load
- Excessive sweating
Regional edema at the site of capillary sampling can cause false low values of cNa+.
For more information, go to Preanalytical considerations.